Conduit and ground wire connected by a metal strap



20, 1968 MITSUJI lCHlKAWA 3,370,122

I CONDUIT AND GROUND WIRE CONNECTED BY A METAL STRAP 4 Sheets-Sheet 1 Filed May 27, 1964 INVENTOR.

Feb. 20,1968 YM|T SUJI lCHlKAWA 3,370,122

CONDUIT AND GROUNDWIRE CONNECTED BY A METAL STRAP Filed May '27, 1964 4 Sheets-Sheet 2 I NVENTOK F 1963 MlTSUJl lCHlKAWA 3,370,122

CONDUIT AN D GROUND WIRE CONNECTED BY A METAL STRAP Filed May 27, 1964 4 Sheets-Sheet 3 MITSUJ) 'IcmnwA INVENTOR.

1963 mrfsuJl ICHIKAWA 3,37

. CONDUIT AND GROUND WIRE CONNECTED BY A METAL STRAP 4 Sheets-Sheet 4 Filed May 27. 1964 INVENTOR.

BY I v United States Patent This invention relates to a wire connecting piece for mounting a ground wire to an electrical conduit or for providing rigid and accurate branch connection of electric wires thereby facilitating mounting and connecting operations thereof.

An object of this invention is to provide a wire connecting piece made of a strap of copper or other metal plate cut in rectangular or other form, comprising an outwardly bent portion formed by outwardly bending one end of the metal plate in L-shaped or other form, and an inwardly bent portion formed by inwardly-bending the other end of the metal plate in hook-like or other form, wherein the metal plate is wound onto an electric conduit, electric wires or the like in such a manner that the outwardly bent portion is disposed in contact with the outer surface of a connecting member and the inwardly bent portion is linearly extended in the direction of a line tan gential to the connecting piece, said inwardly bent portion is retained by said outwardly bent portion, the re tained part is pinched by means of a pinching tool such as pliers, and thereafter the retained part is bent in the bending direction of the outwardly bent portion so that the same is disposed in pressure-contact with the outer surface of the connecting member. The purpose of the wire connecting piece in accordance with this invention resides in that a locus of radius of gyration traced by the outwardly bent portion of the metal plate is located o-utwardly of that traced by the inwardly bent portion thereof by pushing down said inwardly bent portion in the bending direction of the outwardly bent portion, the other end portion of the metal plate is extended and then strongly wound on the connecting member so as to prevent the inwardly bent portion from being buckled by a compression force exerted on the metal plate during the bending of the inwardly bent portion, and the metal plate and the connecting member are disposed in tight contact with each other by destroying rust produced on the connecting member or rust preventives applied thereon, thereby minimizing contact resistance.

Other objects and features of this invention will become more apparent from the following descriptions made with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of the wire connecting piece of this invention, illustrating the same as being extended;

FIGS. 2A, 2B and 2C illustrate the order in which the connecting piece of this invention is wound onto an electric conduit, thereby clamping ground wires;

FIGS. 3A, 3B and 3C illustrate branch connections of electric wires; Y

FIGS. 4A, 4B and 4C illustrate the order in which the ends of the wire connecting piece of this invention are bent;

FIG. 5 is a perspective view of another embodiment of this invention, illustrating the same as being extended;

FIGS. 6A, 6B and 6C illustrate the order in which the wire connecting piece shown in FIG. 5 is wound onto an electric conduit, thereby clamping ground wires;

FIGS. 7A, 7B and 7C illustrate branch connections of 3,370,122 Patented Feb. 20, 1968 "ice electric wires to be obtained by employing the connecting piece shown in FIG. 5;

FIG. 8 is a perspective view of a further embodiment of this invention;

FIG. 9 is a view illustrating the manner in which the wire connecting piece shown in FIG. 8 is wound onto an electric conduit;

FIG. 10 is a front view of the wire connecting piece shown in FIG. 8, illustrating the wire connecting piece when the same is suitably employed;

FIG. 11 is a perspective view of a still further embodiment of this invention; and

FIG. 12 is a perspective'view showing the wire con necting piece when the same is properly used.

The embodiments of this invention will be explained Example I Referring to FIGS. 1 and 2, a metal plate 1 is made of a copper plate or the like which is cut into a rectangular form and has a predetermined thickness. One end of the metal plate 1 is bent outwardly so as to form an L-shaped bent portion 2. An engaging groove 5 for ground wires 3 and 4 is formed so as to extend across the metal plate. In the groove 5 are formed concave and convex portions 6 respectively extending longitudinally of the metal plate. The metal plate is formed with curved surfaces 8 and 9 on the opposite sides of the groove 5 so that the metal plate is snugly fitted on the circumferential curved surface of an electric conduit 7. The other end portion of the metal plate is made approximately straight as at 10 and the outer edge portion thereof is inwardly bent so as to form a hook-like bent portion 11 having the same length as that of the L-shaped bent portion 2.

Reference numeral 12 indicates inwardly directed sharp projections (or longitudinally split cone-like projections).

In order to clamp ground wires 3 and 4 to the electric conduit 7, the ground wires 3 and 4 are first juxtaposed on the outer periphery of the electric conduit 7 so that the ground wires 3 and 4 are disposed axially in parallel with each other, as shown in FIG. 2A, and then the metal plate 1 is wound thereonto by accommodating the ground wires 3 and 4 within the groove 5. Subsequently, the L- shaped bent portion 2 is engaged with the hook-like bent portion 11, as shown in FIG. 2B. In this case, the end of the L-shaped bent portion 2 is engaged with the inner bent part of the hook-like bent portion 11, and the end of the hook-like bent portion 11 is brought to the outer bent part of the L-shaped bent portion 2 so that the L-shaped bent portion 2 is held between the hook-like bent portion 11 and the straight portion so as to form a triple layer portion. This triple layer portion is pinched by means of a clamping tool 12: such as pliers, and further it is pushed in the bending direction of the portion 2 with respect to the corner 2a of the L-shaped bent portion 2 and then flattened as illustrated in FIG. 2C, thus strongly clamping the straight portion 10 with respect to the corner of the L-shaped bent portion 2 so that oxide films, thin enamel coatings, and the like in the contacting portions between the electric conduit 7 and the ground wires 3, 4 and between the metal plate 1, the electric conduit 7 and the ground wires 3, 4 are destroyed, thereby cold pressing these members by exposing their original surfaces. In the case that the films are thick and so rigid as polyethylene, the inwardly directed sharp projections 12, 12 provided on the metal plate 1 cut into the films by clamping the projections 12, 12 to the electric conduit, thereby destroying the film so that the electric conduit 7 and the metal plate 1 are contacted with each other.

This relation will be explained in greater detail with reference to FIGS. 4A, 4B and 40. A locus 20 described by the end of the L-shaped bent portion 2 about the corner 2a thereof is projected outwardly of a locus 11b having a radius equal to the length of the straight portion 10 of the metal plate 1 including the outer diameter 11a of the electric conduit 7, said portion 10 being tangential to the electric conduit 7 (namely, a locus having a radius of gyration equal to the length of the L-shaped bent portion), and the straight portion 10 is pulled over a distance between these loci thus tightly clamping the electric conduit 7, the ground wires 3, 4 and the metal plate 1 together. The triple layer portion can be sufiiciently pushed down by a slight force. This is apparent from the view-point of both dynamics and experiment. Furthermore, the clamping portion of the metal plate becomes a triple layer, therefore, once it is bent, it can not easily be returned to its original state. Since the clamping portion 2 of the metal plate is the Superimposed portion of the triple layer portion, that portion 2 will never be deformed, and the portion of the metal plate wound on the electric conduit is extended by the drag of the compression force, thereby strongly clamping the electric conduit.

FIGS. 3A, 3B and 3C illustrate the case in which a main electric transmission wire 13 and branch electric wires 14 are connected to each other through use of the metal plate 1. In this case, the L-shaped bent portion 2, the straight portion 10 and the hook-like bent portion 11 are likewise superimposed so as to form a triple layer. After this triple layer portion is tightened by strongly gripping the outside thereof by means of cutting pliers or the like, the same is bent in the bending direction of the L-shaped bent portion 2, thus positively maintaining clamped relationship.

According to experiments performed with respect to FIG. 2, it has been found that, when variations in resistance of the contacting portion of the connected ground wires (zinc plating having a coating applied on the surface thereof) and electric conduit are measured and compared by promoting reactions by repeatedly immersing the connected ground wires and electric conduit in a thick salt water (100 grams of salt per 21 of water) and exposing the same twice a day respectively in the case that the contacting portion of the ground wires and the electric conduit is polished and in the case that it is not polished, the contact resistance becomes smaller in the latter case.

This proves that a portion of the metal plate and ground wires tears the surface coating of electric conduit and thus is completely contacted with the whole of the zinc portion.

Example II Referring to FIG. 5 and FIGS. 6A, 6B and 6C, one end of a copper plate 1 is outwardly directed and bent in I-shaped form so as to form a hook portion a, while the other end of the copper plate 1 is inwardly directed and bent in J-shaped form so as to form a clamping portion b. An engaging groove 5 for ground wires 3 and 4 is formed in the intermediate portion of the copper plate I. The electric conduit 7 and the ground wires 3 and 4 are surrounded by the copper plate 1, the end of the clamping portion b is placed in the groove on the end of the hook portion a, and engagement of the two portions a and b is made rigid and positive by gripping the bent portion of the clamping portion b by means of cutting pliers or the like. Thereafter, the extreme end of the clamping portion b is strongly beaten downwardly toward the electric conduit or clamped in the direction indicated by an arrow in FIG. 6B. In this case, since the two sides having two centers (0, d) (the upper and lower sides of the clamping portion b) integrally combines the vortex, thereof, strong forces directed toward each other are exerted onto both centers a, b, and the positions 0, d are approached to each other when the clamping portion b is clamped down by said strong forces. Namely, a strong clamping force results in accordance with the difference of the loci described by both ends when the clamping portion b is deformed, thereby clamping the copper sheet. Consequently, three copper sheets are piled in the hook portion a, so that the copper sheet is extremely deformed from its original shape by further tensioning the side a and, therefore, hardening effect occurs, thereby further increasing the clamping force. Accordingly, when the insulating and rust-preventive film 5' of the electric conduit is thin, the grounding wires 3, 4 destroy the contact portion thereof with the film and closely contact the electric conduit 7. In case that the film is thick and so rigid as polyethylene, an inwardly directed projection or semi-cone shaped (longitudinally split cone shaped) edge 6' provided on the copper plate 1 is cut into the film 5' when the copper plate is clamped onto the electric conduit, thereby destroying the film so that the copper sheet contacts the electric conduit.

FIGS. 7A, 7B and 7C illustrate the case in which electric wires (main wires) 7 and branch wires 8 are connected to each other through use of a copper sheet 1. In this case, too, the extreme end of the clamping portion b is clamped in the inside of the hook portion a, the engagement is made strong by gripping the bent portion of the clamping portion b, and thereafter the clamping portion 12 is downwardly strongly pushed and flattened or deformed and clamped by means of pliers or the like.

In this embodiment, the folded portion of the upper end is extended to form the clamping portion b when the opposite ends of the copper plate are bent, therefore, the clamping portion is never extended, thus eliminating looseness due to vibrations and providing for a high durability.

Example III Referring to FIG. 8, a metal plate 1 is formed approximately into J-shape, one end of which being slightly outwardly bent into U-shape so as to form a retaining portion 2 while the other end thereof being outwardly bent to provide a bent portion which is in turn upwardly curved so as to form a retaining edge 3. Further, the metal plate 1 is provided with a ground wire engaging groove 5 adjacent said retaining edge 3 in convex relationship to the outer surface of the metal plate 1, and said groove 5 has concave and convex fine grooves formed therein for preventing a ground wire 55 from being easily removed when the latter is disposed in clamping engagement with the inner circumference of said groove 5.

In employing this connecting piece, as shownin FIG. 9, the electric conduit 7 is inserted through the connecting piece, the ground wire 5 is inserted in the ground wire engaging groove 5, and thereafter retaining portion 2' is engaged with the retaining edge 3, the engaged part being pressed by means of pliers 12' or the like. Further, as shown in FIG. 10, the engaged part is pressed into contact with the electric conduit in such a manner that the retaining edge 3 is located inside while the engaging portion 2 is located outside so that a locus traced by the retaining portion 2' lies outwardly of that traced by the retaining edge 3', and thus the engaged part is strongly clamped in accordance with the difference between the loci.

In mounting the connecting piece to the electric conduit, it is tedious to employ a different connecting piece in the case that the diameter of the ground wire is slightly different or the diameter of the electric conduit is more or less different, therefore, in this embodiment, it is possible to adjust the clamping of. the connecting piece by outwardly curving the retaining edge 3'.

Example IV Referring to FIGS. 11 and 1-2, a thin rectangular steel plate or a thin copper plate 1 is bent in opposing relation so as to have two arcuate surfaces 22 and 23, the arcuate surface 22 is extended so that a retaining rim 25 is formed by outwardly curving an end rim 22a as indicated at 24, while the other arcuate surface 23 is linearly extended, so that a retaining hook 27 is formed by inwardly curving the other end rim.

In the aforementioned construction, wires 28 and 29 are fitted in the opposed arcuate surfaces 22 and 23 in parallel with each other, the retaining rim 25 is disposed in engagement with the hook portion 27 of the retaining hook 27 thus engaged, retaining rim 25 and,

retaining hooks 27 are downwardly pressed with respect to the end rims 22a and 23a, a recess portion 30 is formed by strongly compressing by means of pliers .(not shown) the central periphery where the extended portion 26 is superimposed on the surface of the retaining rim 25, so that a portion of the connecting piece is forced into a portion of the peripheral surface of the wire 28 or 29, thereby preventing the connecting piece from being returned to its original shape in order to securely clamp the wires 28 and 29.

While preferred embodiments of this invention are illustrated and described, it will be understood that various additional embodiments andmodifications are contemplated and will occur to those skilled in the art without departing from the spirit and scope of the appended claims.

What I claim is:

1. In combination, a conduit, a metal ground wire and a connecting piece surrounding said conduit and said ground wire, said connecting piece consisting of an elongated metal strap initially in the form of a I having a base and a stem, the base being arcuate on a radius equal to that of said conduit held therein, a transverse groove across said base in a central portion thereof providing inner and outer curved base areas, the base end being bent outwardly into an L-shaped flange, the depth of said groove being slightly less than the thickness of said wire, the free end of said stern being bent inwardly to form a hook-shaped flange, said metal ground wire being held in said groove in direct contact with said conduit, means for penetrating insulation on said conduit to provide electrical connection with said ground wire, said stem being bent around said conduit with said hook embracing said L-flange, said hook being crimped and pressing said ground wire into contact with the outer surface of said conduit, the stem of said strap being forcefully bent around said conduit to exert a compressive force between said wire and conduit.

2. The combination according to claim 1 in which a series of alternating concave and convex ribs extend across said groove, said ribs being substantially parallel to the longitudinal axis of said strap, whereby the pressure of said ground wire against said conduit ruptures the insulation thereon and provides electrical contact therebetween.

3. The combination according to claim 1 in which a series of alternating concave and convex ribs extends across said groove, said ribs being substantially parallel to the longitudinal axis of said strap, at least one projection extending inwardly from said stem and penetrating the insulation on said conduit to provide electrical contact between said connecting piece, said conduit and said ground wire.

4. The combination according to claim 1 in which a series of alternating concave and convex ribs extends across said groove, said ribs being substantially parallel to the longitudinal axis of said strap, said crimped together hook and L-fiange bent in the direction of said groove to lie in contact with said base and provide a grip to maintain electrical contact between said ground wire and said conduit.

References Cited UNITED STATES PATENTS 2,423,627 7/ 1947 Tinnerman 339-96 2,786,192 3/1957 Woolley 339-276 1,631,396 6/1927 Beegle 24-20 FOREIGN PATENTS 626,820 5/1963 Belgium.

446,457 1/1948 Canada.

609,061 9/ 1948 Great Britain.

626,243 4/ 1963 Belgium.

LARAMIE E. ASKIN, Primary Examiner. LEWIS H. MYERS, Examiner. H. HUBERFELD, J. R-UGGIERO, Assistant Examiners. 

1. IN COMBINATION, A CONDUIT, A METAL GROUND WIRE AND A CONNECTING PIECE SURROUNDING SAID CONDUIT AND SAID GROUND WIRE, SAID CONNECTING PIECE CONSISTING OF AN ELONGATED METAL STRAP INITIALLY IN THE FORM OF A J HAVING A BASE AND A STEM, THE BASE BEING ARCUATE ON A RADIUS EQUAL TO THAT OF SAID CONDUIT HELD THEREIN, A TRANSVERSE GROOVE ACROSS SAID BASE IN A CENTRAL PORTION THEREOF PROVIDING INNER AND OUTER CURVED BASE AREAS, THE BASE END BEING BENT OUTWARDLY INTO AN L-SHAPED FLANGE, THE DEPTH OF SAID GROOVE BEING SLIGHTLY LESS THAN THE THICKNESS OF SAID WIRE, THE FREE END OF SAID STEM BEING BENT INWARDLY TO FORM A HOOK-SHAPED FLANGE, SAID METAL GROUND WIRE BEING HELD IN SAID GROOVE IN DIRECT CONTACT WITH SAID CONDUIT, MEANS FOR PENETRATING INSULATION ON SAID CONDUIT TO PROVIDE ELECTRICAL CONNECTION WITH SAID GROUND WIRE, SAID STEM BEING BENT AROUND SAID CONDUIT WITH SAID HOOK EMBRACING SAID L-FLANGE, SAID HOOK BEING CRIMPED AND PRESSING SAID GROUND WIRE INTO CONTACT WITH THE OUTER SURFACE OF SAID CONDUIT, THE STEM OF SAID STRAP BEING FORCEFULLY BENT AROUND SAID CONDUIT TO EXERT A COMPRESSIVE FORCE BETWEEN SAID WIRE AND CONDUIT. 